Resistor element



Apr. 10, 1923 INVENTOR Q0/005 A. Brae/fen.

/ ATTORNEY Patented Apr. 10, 1923.-

UNITED STATES 1,451,529 PATENT OFFICE.

QUINCY A. BRACKETT, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VANIA.

RESISTOR ELEMENT.

Application filed August 5, 1919. Serial No. 315,394.

To all whom it may concern:

Be it known that I, QUINCY A. BRACKE'IT, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny, and State of Pennsylvania, have invented a new and useful Improvement in Resistor Elements, of which the following is a specification.

My invention relates to resistor elements and more particularly to elements offering extremely high resistance to the flow of electrical currents.

This application covers the mechanical construction of the resistor element shown but not described in a co-pending application, Serial No, 281,915, of Ralph E. Marbury and assigned to the Westinghouse Electric & Manufacturing Company.

In connection with vacuum-tube radio sets, it is necessary to employ a member of very high electrical resistance as a grid leak. A further adaptation of an extremely high resistance is found in the leakage members that are, at times, connected across condensers. It has been found diflicult to provide resistors having the extremely high resistance necessary and yet occupying a relatively small space. In the cases where this has been accomplished, it has been difiicult to adjust the resistance of the members, either on account of their method of mounting or on account of their fragility.

Furthermore, many resistors of the prior art, while manufactured under identical conditions, have varied widely among themselves and this variability has been subject to change, both with time and with the atmospheric conditions.

The object of my invention is, therefore, to provide a resistor which shall be of extremely high resistance, shall occupy a relatively small space, and the conductance of which may be controlled, adjusted and maintained with a very high degree of accuracy.

In the accompanying drawings, Figure 1 is a sectional view, and Fig. 2 is a sectional view along the line II-II thereof, taken at 90 from that of Fig. 1, of a resistor constructed in accordance with my invention.

One common method of manufacturinga resistor of very high resistance COIISiStS 1n depositing a layer of conducting material on the inside surface of an evacuated tube at two points of which are mounted contact members. This is usually accomplished by the process known as flashing. One serious ob ection to this method of constructing a resistor is that, although the conductivity of the member may be increased as desired, it cannot be decreased, as the process is not reversible, so that, it is adjustable in one direction only. Furthermore, any defect in the aplparatus would require an entirely new tu e.

Another resistor of this general type, also in common use, consists of a resistor element suspended by a wire at each end. These wires pass through openings in the contact members which are mounted at the ends of the tubes and are soldered thereto after the resistor element has been suspended out of contact with the tube by which it is enclosed. The chief objection to this structure is that, after having been assembled, it is impossible to adjust the resistance of the element. Furthermore, any adjustments made with the resistor not connected to the contact members in their operative relationship would be inaccurate, due to the likelihood that handling during assembly might change the resistance as a result of bending the thin stri and breaking the continuity of the deposit thereon.

By my invention, I provide a resistor in which the resistor element is mounted in its final position, without being completely assembled, in such manner that the conductance thereof may be adjusted at will. Furthermore, the element is provided with a durable and replaceable support so that any defect in the element will require replacement of the element only.

Referring in detail to the drawin I show a molded insulating member 3 enc osed within a glass tube or sheath 4 and supported at'the ends of the tube by metallic conducting members 5 and 6 which are held in position by being in threaded engagement with two contact members or metallic projections 7 and 8 molded into the member 3. Before being assembled within the tube, the member 3, together with the inner ends of the contact members 7 and 8, is machined so as to provide a recess having a flat surface in which the conducting members and the insulating member are flush. Within this recess, a resistor element 9, consisting of a flat strip of insulating material impregnated with a conducting substance, such, for example, as india ink having graphite sus pended therein, is mounted, and is attached to the contact members 7 and 8 by' means of screws 10. Intermediate the two contact members, the element 9 is disposed in engagement with the fiat surface of the insuating member 3 so that it is supported, hroughout its entire length, by a at surace.

By reason of the fact that the element 9 is mounted upon a perfectly flat surface, the conductivity thereof may be decreased by so abrading the exposed surface thereof as to remove a portion of the conducting material without injuring the element, and also, if it be desired to increase the conductance, the desired additional quantity of conducting material may be added.

From the drawings and the foregoing description thereof, it will be apparent to those skilled in the art that the element 9 may be mounted in its final position and the resistance thereof adjusted to the desired value before the structure is completely assembled, which value will be exactlythat of the assembled device.

While I have shown but one form of my invention and described in detail but one application of the same, it will be obvious to- 2. In combination with an insulating base, fixed spaced metallic projections embedded in said base, means for attaching a resistor to said projections, and a conducting member for each of said projections.

3. In combination with an insulating base, a recess in said base, fixed metallic spaced projections upon said base and extending through the walls of said recess, and means for attaching a resistor within said recess to said projections. U

4. In combination with an insulating base, a recess in said base, fixed metallic spaced projections upon said base and extending through the walls of said recess, means for attaching a resistor within said recess to said projections, and a protecting sheath for said insulating base.

5. In combination with an insulating base fixed spaced metallic projections upon said base, means for attaching a resistor to said projections, and a protecting sheath for said insulating base.

6. In combination with an insulating base fixed spaced metallic projections upon sai base, means for attaching a resistor to said projections, a conducting member for each of said projections, and a protecting sheath for said insulating base.

Z. In combination with an insulating base, fixed spaced metallic projections upon said base, means for attaching a resistor to said projections, a conducting member for each of said projections, and a protecting sheath for said insulating base, said conducting mlembers holding said protecting sheath in p ace.

In testimony whereof, I have hereunto subscribed my name this 30th day of July,

QUINCY A. BRAOKETT. 

